The present invention relates generally to a storage, and more particularly to a suspension substrate mounted on a suspension, for example, in a hard disc drive (“HDD”).
The HDD typically includes a disc, and a head stack assembly (“HSA”) that supports a head and moves the head to a target position on the disc. The HSA includes a carriage (also referred to as an “actuator,” an “E-block” due to its E-shaped section or “actuator (“AC”) block”), a suspension attached to a support of the carriage (referred to as an “arm” hereinafter), and a magnetic head part supported on the suspension. The magnetic head part includes a fine head core (simply referred to as a “head” hereinafter) that records and reproduces a signal, and a slider that supports the head.
The suspension also serves as a flat spring that compresses the slider against the disc at a predetermined compression force. As the disc rotates, the airflow or air bearing occurs between the slider and the disc, floating the slider from the disc plane. The floating slider is spaced from the disc by a predetermined distance due to a balance between the floating force and the compression force. In this state, the arm rotates and moves the head to (seek for) a target position on the disc, for information reading and writing.
In order to meet the recent demand for the reduced cost and fast transfer, a long tail suspension is used, which extends a suspension substrate that is electrically connected to the head and provided on the surface of the suspension, whereby an end of the suspension substrate is directly connected to a main flexible printed circuit board (“FPC”) fixed onto the carriage. The long tail suspension integrates a conventional trunk FPC that connects the main FPC to the suspension board, with a suspension substrate for impedance matching.
The suspension substrate that is a thin conductive connector plate extends from the magnetic head part along the centerline of the suspension in the longitudinal direction of the suspension, and then turns by 90° to the outside of the suspension. The suspension substrate is fixed onto the suspension. The end of the suspension board again turns by 90° on the side surface of the suspension to make a detour, and forms an aerial section located in air outside to the suspension and the arm. The aerial section extends along the contours of the suspension and the arm. In general, part of the suspension substrate from the aerial section to the main FPC is referred to as a long tail. The suspension substrate including the long tail has a wire pattern on a SUS substrate via an insulating layer. Next, the long tail is inserted into a slit that is formed in the side surface of the arm. Thereafter, the long tail is bent by 90°, and soldered to the main FPC.
Japanese Patent Application, Publication No. 4-111217 provides a bending part to part of the suspension substrate adhered to the suspension, and secures a bending action of the suspension as a flat spring without adhering the bending part (for example, FIG. 4). Japanese Patent Application, Publication No. 4-144186 proposes a slit in an FPC's bending part that connects a liquid crystal panel substrate to a control substrate.
Other prior art include Japanese Patent Applications, Publication Nos. 2003-152404 and 2003-59023.
A connection between the long tail and the main FPC requires an alignment between terminals at the long tail's tip and terminals of the main FPC. However, it is difficult to elongate or shrink the long tail along the longitudinal direction due to the rigidity of the SUS. In addition, while totally four terminals including a pair of terminals for recording and another pair of terminals for reproducing are conventionally necessary for one head, still another pair of terminals for floatation amount control have recently become necessary for precise control over the floatation amount of the slider. On the other hand, a size of a terminal part on which the terminals are formed is maintained due to the limitations from the standard. Therefore, both the long tail and the main FPC are required to squeeze six terminals in the terminal part that conventionally arranges four terminals, and a more precise alignment becomes necessary due to a reduced pitch between the terminals. It is difficult to manufacture an expandable and shrinkable long tail. When a tension applies between the long tail and the main FPC, and the long tail and/or the main FPC would suffer from a lowered characteristic, such as a disconnection.